A few questions about adamantine weapons and whether a something stacks with one of their qualities.

[noble peasant]

The description of what qualities a weapon being made of adamantine gains states this.

"Weapons fashioned from adamantine have a natural ability to bypass hardness when sundering weapons or attacking objects, ignoring hardness less than 20."

It says it ignores hardness less than 20, so if something has 20 or more does it have no effect? Like if something has 20 hardness do I ignore the first 19 of it or does it simply have no effect?

Also what if I have an ability that lets me bypass hardness such as the perfect style untwisting iron feat chain, does that stack with an adamantine weapons ability to bypass hardness?

[Cap. Darling]

If somthing has hardness 20 you dont ignore it and you have to deal with all the hardness. It dosent ignore the first 19 or 20 points it ignorer hardness under 20.

[Just a Guess]

noble peasant wrote:

Also what if I have an ability that lets me bypass hardness such as the perfect style untwisting iron feat chain, does that stack with an adamantine weapons ability to bypass hardness?

I do not think so. If you could actually reduce the hardness it would be different but only ignoring some of it should not help an adamantine weapon.